Teens, Young Adults With Obesity and Type 2 Diabetes Have Carotid Artery Abnormalities

Adolescents and young adults with obesity and type 2 diabetes mellitus have significantly greater carotid intima-media thickness and carotid artery stiffness than their lean counterparts, according to the results of a new study published online May 26 in Circulation.

"Adults with obesity or type 2 diabetes mellitus (T2DM) are at higher risk for stroke and myocardial infarction," write Elaine M. Urbina, MD, from the University of Cincinnati, Cincinnati, Ohio, and colleagues. "Many of these high-risk individuals demonstrate evidence of target organ damage in the carotid arteries (increased carotid intima-media thickness and carotid stiffness) well before the adverse cardiovascular outcomes occur. Whether similar changes in the carotid arteries occur in youth with obesity or T2DM is not known."

Increased Thickness Found in Uncomplicated Obesity

The aim of the study was to determine whether such changes did, in fact, occur in adolescents and young adults with obesity and type 2 diabetes mellitus vs lean control subjects. The study population consisted of 446 youths who were part of an ongoing study of the cardiac and vascular effects of obesity and type 2 diabetes. Their ages ranged from 10 to 24 years; 65% were nonwhite and 39% were male.

The investigators measured carotid intima-media thickness, blood pressure, and anthropometric and laboratory values, and calculated the Young elastic modulus and beta stiffness index in 182 lean subjects, 136 obese subjects, and 128 subjects with type 2 diabetes.

They found that cardiovascular risk factors worsened from the lean group to the obese group to the type 2 diabetes group. Subjects with type 2 diabetes had greater carotid intima-media thickness than lean and obese subjects for the common carotid artery and bulb. For the internal carotid artery, carotid intima-media thickness measurements in both obese subjects and subjects with type 2 diabetes were thicker vs the lean subjects (P = .05 for all). Obese subjects and subjects with type 2 diabetes had stiffer carotid arteries with higher Young elastic modulus and beta stiffness index than lean subjects.

Independent determinants of carotid intima-media thickness were group, group x age interaction, sex, and systolic blood pressure for the common carotid artery (r ² = 0.17); age, race, and systolic blood pressure for the bulb (r ² = 0.16); and age, race, sex, systolic blood pressure, and total cholesterol levels for the internal carotid artery (r ² = 0.21). Age, systolic blood pressure, and diastolic blood pressure were determinants of all measures of carotid stiffness, with sex adding to the Young elastic modulus (r ² = 0.23), and body mass index Z score, group, and group x age interaction contributing to the beta stiffness index (r ² = 0.31; all P < .0001), the study authors report.

The finding that youngsters with type 2 diabetes have significantly thicker carotid intima-media thickness than their lean counterparts is not surprising, the authors write. A more important finding is that this increased thickness can be found in uncomplicated obesity, demonstrating that "early changes in vascular structure and function can be demonstrated in youth with obesity before the development of carbohydrate intolerance."

Study Limitations

Citing the limitations to the study, the authors write that the cross-sectional design of their study did not permit them to determine a time sequence for the development of vascular changes, from uncomplicated obesity to metabolic syndrome to type 2 diabetes. The age range of the cohort was narrow, which may have limited the ability to detect increases in common carotid intima-media thickness in lean subjects. Also, the group with diabetes was slightly older and had higher blood pressure and cholesterol levels than lean and obese subjects.

They also point out that the absolute magnitude of the differences in carotid intima-media thickness between the groups was small. This calls into question the usefulness of measuring carotid intima-media thickness for risk stratification of pediatric patients, which may be diminished by "imprecision of the methodology and biological variability."

Finally, ultrasound screening, which was used to measure carotid intima-media thickness, was limited by a lack of normative data across age, sex, and race/ethnicity. Further refinements in ultrasound techniques and more data in healthy children are needed to advance the field, they write.

With the prevalence of obesity-related metabolic syndrome and type 2 diabetes increasing across the globe, pediatric healthcare practitioners should continue to screen for abnormalities in cardiovascular risk factors, especially in obese and diabetic children. "Comprehensive lifestyle interventions to reduce obesity must be applied now if we are to prevent a projected decline in life expectancy for our youth," the study authors conclude.